Centrifugal Compressor Oil Return via Bent Pressure Relief Passage

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Solution Overview

Problem

Centrifugal compressors face a reduction in the amount of oil supplied to the speed increaser due to bubble accumulation and leakage through pressure relief passages, which affects the efficiency and reliability of the compressor.

Innovation Solution

The design incorporates a pressure relief passage system with a merging portion and a bent portion to separate gas and liquid, where bubbles are crushed, and the oil is returned to the oil pan, while gas is discharged externally, preventing oil leakage and maintaining oil supply to the speed increaser.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stress or pressure

If a pressure relief passage is provided to limit pressure increase in the speed increaser chamber, then pressure control is improved, but oil may leak out with bubbles causing reduction in oil supply amount

Engineering Contradiction:

Improvepressure in speed increaser chamberVSAvoidamount of oil supplied to speed increaser

Core Design Contradiction:

Stress or pressureVSQuantity of substance

Solution Approach 1:

The pressure relief passage is divided into two separate passages: a first pressure relief passage for discharging bubbles and a second pressure relief passage for discharging oil. This segmentation allows selective discharge of different substances, preventing oil loss while maintaining pressure control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A gas-liquid separator is introduced as an intermediary component in the pressure relief system. This separator distinguishes between gas (bubbles) and liquid (oil) phases, directing each to its appropriate discharge pathway and preventing mixed discharge that would cause oil loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If oil is supplied to the speed increaser to reduce friction and prevent seizure, then lubrication is improved, but bubbles generated in the oil may accumulate and cause oil leakage through the pressure relief passage

Engineering Contradiction:

Improvelubrication of speed increaserVSAvoidoil leakage through pressure relief passage

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A bubble removal mechanism utilizing porous materials or bubble breakers is employed to separate and remove gas bubbles from the oil before the oil reaches the pressure relief passage, preventing bubble-induced oil leakage.

Inventive Principle:

Principle #31Porous materials

3Productivity

If the impeller rotates at high speed to compress gas, then compression performance is improved, but pressure difference between impeller chamber and speed increaser chamber increases causing oil leakage

Engineering Contradiction:

Improvegas compression performanceVSAvoidoil leakage from speed increaser chamber to impeller chamber

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

A seal member is introduced as an intermediary component between the speed increaser chamber and impeller chamber. This seal member prevents direct leakage of oil through the gap, maintaining oil quantity even when pressure differences occur during high-speed operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively limits the reduction in oil supplied to the speed increaser, enhancing the compressor's efficiency and reliability by preventing bubble-induced oil leakage and ensuring consistent lubrication and operation.

Implementation Method 1

The bent portion is configured to perform gas/liquid separation by crushing bubbles

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

The seal member prevents leakage of the oil stored in the speed increaser chamber into the impeller chamber through the insertion hole

Methodology Applied

Scientific EffectSealing:

Implementation Method 3

The oil supplied to the speed increaser reduces friction and prevents seizure in sliding portions of the high speed shaft and the speed increaser

Methodology Applied

Scientific EffectLubrication: Lubrication

Data Source

PatentUS11448234B2Centrifugal compressor

Publication Date: 2022.09.20 TOYOTA INDUSTRIES CORP

AI summary

First and second pressure relief passages extend from an oil pan in a branching manner, and merge with each other to form a merging portion. A pressure relief hole is arranged above the merging portion, and a first pressure relief passage is arranged below the merging portion. The minimum cross-sectional area of the second pressure relief passage is smaller than the minimum cross-sectional area of the first pressure relief passage. The second pressure relief passage includes a bent portion formed by bending the second pressure relief passage. The bent portion is configured to perform gas/liquid separation by crushing bubbles. When reaching the merging portion from the bent portion, oil is returned to the oil pan via the first pressure relief passage. When reaching the merging portion from the bent portion, gas is discharged to the outside of the housing via the pressure relief hole.